1. Field of the Invention
The present invention relates to an exhaust gas purifying filter for purifying an exhaust gas, by collecting particulates from the exhaust gas of an internal combustion engine, and a method for manufacturing the same.
2. Description of the Related Art
Conventionally, an exhaust gas purifying filter having a ceramic honeycomb structure acts as an exhaust gas purifying filter, for purifying an exhaust gas, by collecting particulates from the exhaust gas of an internal combustion engine.
The ceramic honeycomb structure comprises a surrounding wall, partition walls provided in a honeycomb pattern within the surrounding wall, and a plurality of cells partitioned by the partition walls and, at the same time, penetrating through from one end face of the ceramic honeycomb structure to the other.
In order to improve the efficiency of purification of the exhaust gas purifying filter, it is desired to make the partition walls thinner and to increase the porosity in the surrounding wall and the partition walls. However, if the partition wall is made thinner and the porosity is increased, the mechanical strength of the ceramic honeycomb structure is reduced. Therefore, a problem arises that the end portions of the ceramic honeycomb structure become more likely to fracture when catalysts are provided, when the structure is attached to an internal combustion engine, or the like.
In order to solve this problem, a ceramic honeycomb structure, whose cells in the vicinity of the peripheral portion are filled with plug material, has been proposed (for example, refer to Patent References 1 and 2).
[Patent Reference 1]
Japanese Examined Patent Publication (Kokoku) No. 63-12658
[Patent Reference 2]
Japanese Unexamined Patent Publication (Kokai) No. 7-246341
However, no definition is given as to the range of the peripheral area to be filled with the plug material in the conventional ceramic honeycomb structure. If the range of the peripheral area to be filled with the plug material is too large, a problem arises that the exhaust gas filtration area decreases and, at the same time, the pressure loss increases. On the other hand, if the peripheral area to be filled with the plug material is too small, it is not possible to secure a sufficient strength of the ceramic honeycomb structure.
Therefore, it is difficult to obtain an exhaust gas purifying filter having a high strength and an excellent efficiency of purification only by filling the vicinity of the peripheral portion with plug material.